
                      UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                          SECTOR POLICIES AND PROGRAMS DIVISION
                       OFFICE OF AIR QUALITY PLANNING AND STANDARDS
                               OFFICE OF AIR AND RADIATION


November 22, 2011

MEMORANDUM

SUBJECT:	Summary of Pulp Bleaching Technology Review
	
FROM:	Kelley Spence	(EPA/OAR/OAQPS/SPPD/NRG)
      John Bradfield (EPA/OAR/OAQPS/SPPD/NRG)
		
TO:		Docket EPA-HQ-OAR-2007-0544


This memorandum summarizes the technology review of bleaching technology in pulp mills subject to 40 CFR 63, subpart S analyzed for the Risk and Technology Review (RTR) of the National Emission Standards for Hazardous Air Pollutants (NESHAP) for the pulp and paper industry. 
                                       
Background[1][,2]:

   Bleaching is the whitening of pulp utilizing a chemical treatment; bleaching can be lignin preserving or lignin removing, based on which chemicals are used for treatment.  Lignin preserving is commonly used for mechanical and secondary pulps, as they are used to produce products of which brightness is not always required, such as newspapers.  Bleaching that removes lignin is typically used for higher grades of paper, such as printing and writing grades, where brightness has a significant impact on the final product properties. 
   Bleaching is performed in a continuous sequence of processing which involves chemical treatment, chemical extraction, and washing.  Bleaching chemicals include the following: chlorine (C), hypochlorite (H), alkaline extraction (E), chlorine dioxide (D), oxygen (O), peroxide (P), ozone (Z), and enzymes (X).  These chemicals are used in sequence to obtain the desired product brightness. For example, a sequence for a highly bleached sheet could be OD(EOP)DD, representing oxygen delignification, followed by chlorine dioxide, enriched extraction with oxygen and peroxide, followed by two more chlorine dioxide stages. The process involves mixing the pulp and bleaching chemicals, reaction of the chemical in a retention tower, and removal of the chemical by washing the pulp.  Washing is typically performed between each stage, to remove chemicals prior to the following stage.  An example of this sequence is shown in Figure 1.
   
   
   
   
   
   
   
                  Figure 1: Bleaching line sequence OD(EOP)DD
   
   
   Prior to the original NESHAP, chlorine was used for bleaching. It was replaced by most facilities with chlorine dioxide to meet effluent guidelines and federal water rules after promulgation of "The Cluster Rule" (a simultaneous publication of Federal water and air pollution control regulations for the pulp and paper industry).  
   Subpart S requires mills to collect and control bleaching process vent emissions from stages utilizing chlorinated compounds with a caustic scrubber and to eliminate the use of certain bleaching chemicals (chlorine and hypochlorite) from kraft, sulfite, and soda pulp bleach plants. In this definition, a stage consists of a retention tower, washers, seal tanks, chemical and steam mixers, and vacuum pumps. There are three alternative emission limits for total chlorinated HAP (excluding chloroform): 
   1. Reduce chlorinated HAP emissions by 99% weight 
   2. Achieve a total outlet mass emission rate less than or equal to 0.002 pounds chlorinated 
       HAPs per ton oven-dried pulp for all subject stages
   3. Achieve an outlet concentration of chlorinated HAPs less than or equal to 10 ppmv     
For chloroform, subpart S requires elimination of the use of chlorine and hypochlorite, or compliance with the applicable effluent limitations guidelines and standards in 40 CFR 430.



Developments in Practices, Processes, and Control Technologies

2011 Information Collection Request (ICR)  -  Part 1 Technologies
   The Information Collection Request (ICR)[3] collected data from the major and synthetic minor pulp and paper source facilities in the US.  Of these respondents, 98 facilities reported (in the bleaching tab of the survey) that they perform pulp bleaching with 164 bleaching lines. Elemental chlorine free (ECF) processing was used in 104 bleaching lines, while totally chlorine free (TCF) was used in 31 lines, and processed chlorine free (PCF) was used in 22 lines.  The remaining 7 lines utilized peroxide, sodium sulfate, hypochlorite, chlorine, or a combination of these bleaching chemicals. Oxygen delignification was utilized on 42 of the ECF bleaching lines to reduce emissions and bleaching chemical cost and consumption. Review of the survey data also showed 2 major source facilities, subject only to the effluent guidelines referenced in section 63.445(d)(1) that utilize chlorine as a bleaching agent and 2 that utilize hypochlorite. Options were not recommended for ending the use of chlorine and hypochlorite at these facilities, as it would be a change to the effluent guidelines, not the air regulations.               
   There were 108 reported scrubbers in the Part I database. Packed-tower caustic scrubbers were the most popular type of air pollution control device used to collect and reduce emissions.  Packing material was typically saddles made of polyvinyl chloride (PVC) and emissions reductions were reported at greater than 99%. White liquor, weak wash, and sodium hydroxide with fresh water were commonly reported as the source of liquid for the scrubber.    

               Table 1: Summary technologies from ICR part I review
                                       
                             Number of Facilities
Facilities performing bleaching
                                      98
Bleach lines
                                      164
      ECF (elemental chlorine free)
                                      104
      TCF (totally chlorine free)
                                      31
      PCF (processed chlorine free)
                                      22
     Other
                                       7
O2 delig pretreatment
                                      42


Facilities (59) provided bleach plant scrubber test reports for chlorine and chlorine dioxide with their Part I ICR responses.  The common test methods were EPA M26A and NCASI 520 & 548.  The majority of tests were performed once to show compliance, however, several permitting authorities required testing annually or every five years (once per permit cycle).

Review of RBLC
   Review of the RBLC identified two facilities (RBLC ID: OK-0112 and WI-0205) with VOC BACT-PSD control methods for bleaching.  The facility in Oklahoma utilized bleaching using no chlorine or chlorine dioxide; the facility in Wisconsin conducted mechanical bleaching with only hydrogen peroxide, sodium hydrosulfite, and sodium borohydride[4].  
                                         
Review of Other Available Information
   The Multi-Pollutant Emission Reduction Analysis Foundation (MERAF) for the Pulp and Paper Sector report was reviewed for additional information[5].  The report was prepared by AMEC Forest Industry Consulting for Environment Canada and The Canadian Council of Ministers of Environment (CCME). This report identifies the current best design for chlorine dioxide generation as venting miscellaneous vents from the process through a tail gas scrubber and to use the tail gas packed tower scrubber (using chilled water) after the chlorine dioxide absorption tower to reduce air emissions.
   Mills that use Chlorine Dioxide (ClO2) for bleaching must generate it on site since it is unsafe to transport.  A review of the air permits collected under Part I of the ICR indicates that the control technology discussed above, caustic scrubbing, is typical for the control of chlorinated compounds from ClO2 generation units and is equally effective (i.e. 99%+).  Because similar technology is also required for bleaching vents employing chlorinated compounds under Subpart S, facilities can employ a common scrubber for both processes instead of a stand alone scrubber.
                                         
Available HAP Emissions Data:

   Substantial HAP emissions reductions were achieved through the implementation of subpart S for beaching vents. HAPs from this process originate in the incoming pulp or from side reactions that occur during bleaching.
   
2011 Information Collection Request (ICR)  -  Part II Data
   A total of approximately 2,600 tons of HAP per year are emitted from bleaching, according the ICR Part II data collected. The average amount emitted from these facilities is approximately 38 tons per year. 

NCASI Data
   Toxic air emissions from kraft mill bleach plants were tested and reported by NCASI (Technical Bulletin No. 973, page 15-25), mean emission factors are presented in Table 2. Of the United States facilities tested, only 5 of 54 were either ECF or TCF facilities. All facilities tested in Canada (6) were ECF mills. This means that the emission factors shown in Table 2 are limited in their representation of chlorinated HAPs from mills utilizing ECF or TCF bleaching. Also noted is that chloroform is formed at approximately 0.3  -  3.0 lb/ODTP in hypochlorite bleaching; ECF mills, however, only produce 0.005 lb/ODTP. The quality of bleach plant scrubber shower water and type of wood are thought to have an impact on VOC compounds from the bleach plant. 
   











                  Table 2: Summary of air toxic emissions from 
                     kraft mill bleach plants (NCASI TB 973) 
   
                                   Pollutant
                                    Non-ECF
                             Emissions (lb/ADTBP)
                                    Non-ECF
                                No. of Sources
                                     ECF 
                             Emissions (lb/ADTBP)
                                     ECF 
                                No. of Sources
Acetaldehyde
                                   1.64E-03
                                      39
                                       
                                       
Acetone
                                   3.70E-03
                                      47
                                       
                                       
Acetophenone
                                      --
                                      15
                                       
                                       
Acrolein
                                   6.23E-05
                                      15
                                       
                                       
Acrylonitrile
                                  <1.3E-04
                                       1
                                       
                                       
Aniline
                                  <3.7E-08
                                       1
                                       
                                       
Benzaldehyde
                                   2.80E-04
                                      12
                                       
                                       
Benzene
                                   5.74E-05
                                      42
                                       
                                       
Biphenyl
                                      --
                                       3
                                       
                                       
Bromodichloromethane
                                   3.70E-03
                                       8
                                       
                                       
Bromomethane
                                  <6.4E-04
                                       1
                                       
                                       
1,3-Butadiene
                                   4.94E-05
                                       6
                                       
                                       
Carbon Disulfide
                                   1.11E-04
                                       5
                                       
                                       
Carbon Tetrachloride
                                   1.92E-04
                                      16
                                   5.06E-06
                                       2
3-Carene (sftwds)
                                   4.72E-03
                                      10
                                       
                                       
3-Carene (hdwds)
                                      --
                                       3
                                       
                                       
Catechol
                                  <8.4E-08
                                       1
                                       
                                       
Chlorobenzene
                                   9.30E-04
                                      14
                                   1.07E-05
                                       8
Chloromethane
                                  <8.8E-04
                                       1
                                       
                                       
m-Cresol
                                      --
                                       2
                                       
                                       
o-Cresol
                                   2.68E-03
                                       5
                                       
                                       
Cresols (mixed isomers)
                                      --
                                      --
                                       
                                       
Crotonaldehyde
                                   6.20E-05
                                       2
                                       
                                       
Cumene
                                   2.20E-04
                                       
                                       2
                                       
                                       
Cyclohexanone
                                   9.40E-05
                                       
                                       5
                                       
                                       
p-Cymene (sftwds)
                                   3.84E-04
                                       
                                       5
                                       
                                       
p-Cymene (hdwds)
                                      --
                                       
                                       3
                                       
                                       
1,2-Dibromoethane
                                   2.33E-04
                                       
                                       3
                                       
                                       
1,1-Dichloroethane
                                  <9.7E-05
                                       
                                       1
                                       
                                       
1,2-Dichloroethane
                                   6.90E-05
                                       
                                      13
                                            --
                                            8
1,1-Dichloroethene
                                  <1.8E-03
                                       
                                       1
                                       
                                       
1,2-Diochloropropane
                                  <9.1E-05
                                       
                                       1
                                       
                                       
1,2-Dichloroethylene
                                   3.20E-04
                                       
                                      13
                                         9.30E-06
                                            7
1,2-Dimethoxyethane
                                      --
                                       
                                       3
                                       
                                       
Ethanol
                                   2.50E-03
                                       
                                      24
                                       
                                       
Ethyl Benzene
                                   8.00E-06
                                       
                                       3
                                       
                                       
Formaldehyde
                                   6.21E-04
                                       
                                      30
                                       
                                       
Hexachlorocyclopentadiene
                                   4.34E-03
                                       
                                       1
                                       
                                       
Hexachloroethane
                                      --
                                       
                                       6
                                          2.50E-02
                                             1
n-Hexane
                                   2.80E-05
                                       
                                      12
                                       
                                       
Hydrochloric Acid
                                   2.30E-02
                                       
                                       7
                                       
                                       
Iodomethane
                                  <5.3E-05
                                       1
1


Isopropanol
                                   1.48E-03
                                      17
17


Limonene (sftwds)
                                   5.20E-04
                                       
1


                                   Pollutant
                             Emissions (lb/ADTBP)
                                No. of Sources
                                     ECF 
                             Emissions (lb/ADTBP)
                                     ECF 
                                No. of Sources
Limonene (hdwds)
                                      --
                                       
1


Methanol
                                   1.62E-01
                                       
57


Methyl Ethyl Ketone
                                   1.40E-03
                                       
48


Methyl Isobutyl Ketone
                                   7.56E-04
                                       
24


Methylene Chloride
                                   1.69E-03
                                       
33
        1.67E-04
               7
Napthalene
                                      --
                                       
4


Phenol
                                   4.96E-03
                                       
17


Alpha-Pinene (sftwds)
                                   1.60E-02
                                       
24


Alpha-Pinene (hdwds)
                                   5.83E-03
                                       
7


Beta-Pinene (sftwds)
                                   6.39E-03
                                       
23


Beta-Pinene(hdwds)
                                   2.14E-03
                                       
5


Propionaldehyde
                                   7.01E-04
                                       
8


Styrene
                                   2.04E-04
                                       
22


Terpenes (sftwds)
                                   3.18E-02
                                       
9


Terpenes (hdwds)
                                   7.70E-03
                                       
8


Alpha-Terpineol
                                      --
                                       
2


Tetrachloroethylene
                                   3.74E-04
                                       
10
             --
              7
Toluene
                                   2.37E-04
                                       
23


1,2,4-Trichlorobenzene
                                   2.73E-03
                                       
14
        1.45E-04
              6
1,1,1-Trichloroethane
                                   2.11E-04
                                       
13
             --
              8
1,1,2-Trichloroethane
                                   2.66E-04
                                       
13
        6.85E-06
              1
Trichloroethylene
                                   4.43E-04
                                       
21
        9.70E-06
              4
Valeraldehyde
                                   5.10E-04
                                       
6


m-,p-Xylene
                                   1.93E-04
                                       
12


o-Xylene
                                   1.03E-04
                                       
12


Xylenes (mixed)
                                   2.17E-04
                                       
21


VOCs as C
                                   1.03E-01
                                       
34


   
   
Review of Other Available Data
   The Multi-Pollutant Emission Reduction Analysis Foundation (MERAF) for the Pulp and Paper Sector report was reviewed for additional data (i.e., Canadian data).  A summary of the estimated emissions are shown in Table 3 for emission points in the bleaching process, based on stage chemical type. As expected, the chlorine and hypochlorite bleaching stages emit significantly more HAP than the extraction and the chlorine dioxide stages. 
   
   
   
   
   
   
   
   
   
   
   
            Table 3: Summary of estimated emissions from MERAF (kg/t)
Emission Point
Total HAP[a]
Chloroform
Chlorine 
Methanol
C-stage tower
0.054-0.252
0.0009-0.01
0.05-0.21
0.00062-0.029
C-stage washer
0.062-0.647
0.0009-0.0113
0.05-0.21
0.009-0.415
C-stage seal tank
0.0084-0.323
5.5E-5 - 7.2E-4
0.00127-0.0053
0.0067-0.311
E-stage tower
0.013-0.026
0.0014-0.01
0-0.003
0.0027-0.0054
E-stage washer
0.031-0.168
0.0014-0.01
0-0.003
0.0035-0.078
E-stage seal tank
0.013-0.101
0.00009-0.0005
0-0.000076
0.0026-0.029
D-stage tower
0.011-0.036
0.00003-0.02
0.01
0.0002
D-stage washer
0.01-0.06
0.00003-0.02
0.01
0.00001-0.003
D-stage seal tank
0.0005-0.02
0.000003-0.001
0.0003
0.000008-0.002
H-stage tower
0.088-0.62
0.04-0.05
0.01
0.00049-0.0063
H-stage washer
0.15
0.04
0.01
0.091
H-stage seal tank
0.074
0.003
0.0003
0.068
Acid sewer 
0.12-0.52
0.008-0.005
0
0.05-0.5
Caustic sewer 
0.041-0.032
0.002-0.0023
0
0.03-0.3
                                         
Regulatory Options:
   
   Section 112(d)(6) of the CAA requires EPA to review and revise the MACT standards, as necessary, taking into account developments in practices, processes, and control technologies. The information presented in this memorandum is relevant for consideration in the development of regulatory options under 112(d)(6).
   As explained in the previous sections of this memo, bleach plant chlorinated vent gas emissions are effectively controlled at 99%.  Our technology review did not identify any new control technologies that had been installed to reduce emissions further beyond the current requirement to control 99%+ at bleaching vents where chlorinated bleaching compounds are used. It is the staff recommendation not to amend the current NESHAP regarding bleach plant vents. 
                                         
References:

1. Pulp and Paper NESHAP: A Plain English Description. U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards.  EPA-456/R-98-008. November 1998.
2.  Smook, G. Handbook for Pulp & Paper Technologists.  3[rd] Edition. Angus Wilde Publications Inc., Bellingham WA.  2002. 
3.   Pulp and Paper ICR 2011.
4.  Memorandum from T. Holloway, C. Gooden, and K. Hanks, to J. Bradfield and B. Schrock, EPA.  Summary of RBLC and Other Findings to Support Section 112(d)(6) Technology Review for Pulp and Paper NESHAP. RTI. 2011.
5.  Multi-pollutant Emission Reduction Analysis Foundation (MERAF) for the Pulp and Paper Sector. AMEC Forest Industry Consulting. 2002.
